A4 - AAV Vectors - Preclinical and Proof-of-Concept In-Vivo Studies (Excluding Non-Human Primates)
24: AAV9 Delivered Artificial microRNAs Effectively Improves GFAP Pathology and Motor Impairment in an Alexander Disease Rat Model
Type: Oral Abstract Session
Presentation Details
Session Title: AAV Vectors - Preclinical and Proof-of-Concept: Therapy Focus
Alexander disease (AxD) is a type of rare neurodegenerative disease known as leukodystrophies. AxD is caused by dominant gain-of-function mutations in the glial fibrillary acidic protein (GFAP) gene and occurs in approximately one in one million births. The disease is progressive and fatal, ranging from infancy to adulthood. GFAP is mainly present in astrocytes of the central nervous system (CNS) and plays an important role in controlling myelination. Mutations in GFAP result in the overproduction and accumulation of the mutant form of GFAP, which causes the formation of Rosenthal fibers, the histopathological hallmark of AxD throughout the CNS. Currently, there is no therapy available to treat AxD. Thus, silencing mutant GFAP could be an attractive therapeutic approach. We have previously developed a scAAV9 vector (scAAV9-GfaABC1D-amiR-GFAP) expressing an artificial microRNA (amiR) to target the conserved GFAP sequences among mice, rats, NHPs and humans. The amiR expression directed by the native promoter of the human GFAP gene (GfaABC1D) was able to downregulate GFAP gene expression and effectively reduce Rosenthal fibers in the AxD mouse brains. However, the mouse model does not show the apparent leukodystrophy and the severity of the human disease phenotypes. Thus, we tested our scAAV9-GfaABC1D-amiR-GFAP in an AxD rat model which recapitulates the whole spectrum of severe features of the AxD syndrome, including high amounts of GFAP accumulation, widespread Rosenthal fibers formation throughout the brain and spinal cord, myelin deficits, motor impairment, failure to thrive and increased mortality. We injected scAAV9-GfaABC1D-amiR-GFAP into three-week-old AxD rats (Gfap+/R237H) by intravenous administration at a dose of 2.0 x e14 genome copies/kg. We found that the treated AxD rats started gaining body weight from three weeks post-injection compared to the untreated AxD rats. Four weeks later, the treated AxD rats showed significant improvements in the rotarod, grip strength and performance in the horizontal ladder test when compared to the untreated animals. In addition, histopathologic analysis showed significant reductions of Rosenthal fibers in whole brain of treated AxD rats. Reduced hyperintense signals (i.e. signs of brain edema) on T2 MRI imaging were observed in the treated AxD rat brains as well. Western blot revealed that GFAP protein levels were reduced after four weeks post-injection. Furthermore, the treated AxD rats continue to show improved performances in motor function tests at 12- and 36-weeks post-injection. Taken together, our data indicates that astrocyte-restricted gene silencing is a promising strategy for efficient and sustainable treatment of AxD and potentially other gain-of-function diseases that affect astrocytes. G.G. and J.X. are corresponding authors.
Wassamon Boonying, Guangping Gao, Jun Xie
Horae Gene Therapy Center, University of Massachusetts Chan Medical School, Worcester, MA"
Find This Session